simplified protocol and implemented text_message::receive()

text_message.h

@@ -2,6 +2,7 @@
 
 #include "message.h"
 #include <string>
+#include <iterator>
 
 
 
@@ -18,6 +19,8 @@ public:
     text_message();
     text_message(std::string);
 
+    std::string get_text();
+
     virtual void receive(boost::asio::ip::tcp::socket&) override;
 
     virtual ~text_message() override;